You make a very good point. I never really explicitly thought about the context in which these jokes tend to be acceptable (i.e. South Park, Cards Against Humanity).
I’m definitely not sure this was accidental stupidity, but it could have been someone who honestly didn’t understand when that sort of thing is “ok” (inasmuch as it can be). Wouldn’t be surprised if a 4chan shut-in assumed that the whole world converses like people online do and did something stupid like this… (also, I’m now left wondering if all of the cards were supposed to be in that faux-not-faux-offensive style)
I absolutely agree an apology is in order, and to some degree the YRs did that, I guess. Whether that was heartfelt is a bit more dubious. Hopefully the specific person responsible will do so as well.